PITTSBURGH -- The Steelers' starting quarterback this weekend will be a player who was cut last weekend or another who was all but ignored during training camp.

No matter, Steelers coach Mike Tomlin said Tuesday. Either Byron Leftwich or Charlie Batch will be expected to play well enough to win until Ben Roethlisberger returns from his four-game suspension.

The Steelers' once quarterback-heavy roster thinned out even more Tuesday when Dennis Dixon was lost indefinitely with a torn meniscus in his left knee. Dixon is expected to have surgery Wednesday and could go on injured reserve, which would end his season after two starts -- and two victories.

Dixon's injury turned out to be more serious than suspected Sunday, when Tomlin said the quarterback could have re-entered a 19-11 victory at Tennessee to hand the ball off if necessary.

Dixon was hurt while scrambling for 21 yards late in the first quarter. He stayed in for two more plays, including an 8-yard run, then was lifted on the next possession and didn't return.

"He planted his leg in the ground and cut inside, and said it felt a little unstable at that point," Tomlin said Tuesday. "Adrenaline and things of that nature, particularly when it's a nonimpact injury, it takes a while before you realize that something's amiss."

The fear of exposing Dixon to injury while running was one reason he was limited him to just a couple of carries in the season-opening 15-9 victory over the Atlanta Falcons.

Because Leftwich still was recovering from a sprained medial collateral ligament in his left knee -- he was cut Saturday to free up a roster spot, then returned Monday -- Batch played the final three quarters at Tennessee. It was Batch's first extensive game action since 2007.

Batch was Pittsburgh's No. 4 quarterback during voluntary workouts and training camp and received almost no work with the starters before playing against the Titans. If Leftwich hadn't been hurt in the Sept. 2 preseason finale, Batch might have been cut.

Now, there's a chance Batch could start this Sunday against the Tampa Bay Buccaneers if Leftwich's knee can't hold up in practice, although Tomlin expects it will be fine.

"He's been able to comfortably get through some workouts," Tomlin said. "Workouts are different from practice, of course, and games, particularly the unanticipated movements that come with football, but we feel comfortable with where he is. We're going to proceed through the week and see how this thing sorts out."

The Steelers traded with the Bucs to reacquire Leftwich immediately after Roethlisberger was suspended in April for violating the NFL's personal-conduct policy.

Leftwich was the backup when the Steelers won the Super Bowl two seasons ago and has an extensive knowledge of the team's playbook. He also throws long passes better than Batch, and starting him would increase the chances of involving deep-threat receiver Mike Wallace in an offense that has yet to score a touchdown in regulation.

The Steelers beat Atlanta 15-9 on Rashard Mendenhall's 50-yard touchdown run in overtime, and their only scoring in Tennessee came on four field goals by Jeff Reed and an Antonio Brown kickoff return.

The Steelers also might be without right guard Trai Essex (ankle) against Tampa Bay (2-0). If Essex can't start, undrafted free agent Doug Legursky would start.

Nose tackle Casey Hampton, held out of the Tennessee game with a hamstring injury, could be ready to play.

Tomlin, meanwhile, backtracked slightly from his post-game comments that the news media underestimated how well the Steelers were capable of playing under adverse circumstances without Roethlisberger. Tomlin suggested comments that the Steelers would be 2-2 or 1-3 without their top quarterback were highly motivational.

"We are emotional beings and sometimes we lose out to that," Tomlin said. "It was probably unwarranted, but that's where I was at that point. It's a tough game. ... We're going to try to have a thicker skin and proceed with business this week, and I'm talking about myself."